On Thu, 2007-02-15 at 19:27 -0600, Mike McCarty wrote: > Sergio Cuéllar Valdés wrote: > > 2007/2/15, Siju George <sgeorge.ml@gmail.com>: > > > > Hi, > > > > maybe you should read about LVM [1]. It is not about file systems, but > > it can help you :) > > I'd rather deal with a case of the Clap. > > LVM is worse than useless for most installations. It makes > the entire file system dependent on every drive in the Logical > Volume working. If any drive fails, then the entire FS becomes > corrupt. As you may know, as the number of devices goes up, > the MTBF goes down drastically, and the probability of failure > goes up dramatically. If one has a largish RAID, then LVM makes > sense, but without RAID or some other error correcting ability, > LVM makes the likelihood of a file system failure increase, and > makes the likelihood of recovery from it decrease, since the > normal recovery tools won't work. It depends on how you use LVM. If you use LVM with Logical Extents with Physical Extent mirroring (or redundant PE) it works just fine with failure modes. Also, most people ignore those noises portending a failure and continue on as if nothing is going on. LVM has come from the "Enterprise" world where you typically don't want to be tied down with partitions. (Netware 5 and below were bad with that). Or basically you want to be able to incrementally add Extents to a Logical Volume as it is needed. It allows you to dole out space to various file systems without worrying about massive disk sub-system upgrade. Also, if you are able to add another disk to your Volume Group that is as big or larger than the failing (note I said failing not failed) you can migrate everything off the the failing disk to the newly added disk. Thereby saving you much headache. There are many benefits to LVM, not just your view of the failure modes. Those failure modes are common for *ANY* disk sub-system, BTW. And RAID does not mean GOOD EVEN DURING FAILURE. I just had a call a month ago to recover a failed 4-way mirrored system. 2 - RAID1 arrays in a RAID1 array (or 4 disks all the same data). The company kept silencing the alarm. Well 3 months since the last one... they had been running on a single disk for that long. OOPS. Not a good backup of it either. Just because you haev RAID, doesn't mean JACK. If you don't pay attention its useless. -- greg@gregfolkert.net Novell's Directory Services is a competitive product to Microsoft's Active Directory in much the same way that the Saturn V is a competitive product to those dinky little model rockets that kids light off down at the playfield. -- Thane Walkup
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